The use of laminating machines to apply laminate material to such items as menus, place mats, and the like for their protection and increased durability has been common practice for many years. In the mass production of such articles, generally opaque sheets having artistic or informational indicia thereon are laminated between continuous webs usually made of transparent material. In some instances, the borders or margins of the successive sheets are in abutment forming a continuous web of abutting laminated sheets. In other instances, the leading and trailing edges of the opaque sheets are separated from each other by the transparent laminate web material. The present invention applies to the latter web format. Cutting and trimming machines using cutting blades are used to slit such laminated web material along the leading, trailing and side edges of the laminated sheets to separate the individual sheets from the transparent web material to which they are laminated.
Some prior art machines use the opacity of the articles and the transparency of the laminate web material between the sheets to trigger a cutting operation. A single light source and a single light sensor device are placed on opposite sides of the continuous webs of laminated material. Preferably, the light source and light sensor device are placed at a location proximate to the cutting blade.
When the opaque sheets pass between the light source and light sensor, the light beam is interrupted. The passage of the leading edge of a sheet between the light source and sensor initiates such interruption. the passage of the trailing edge thereof terminates such interruption. Either transition can trigger an electronic control device to time control the cutting action of a punch or blade at an appropriate time to sever the leading and trailing edges of the sheets from the rest of the laminate web material.
It is obviously aesthetically preferable that the cutting operation be along and parallel to the edges of the sheets either in alignment with the edges or slightly outward or inward thereof if trimming is desired. This requires the leading and trailing edges of the sheets to be parallel to the cutting blade which cuts along the leading and trailing edges of the sheets. Frequently, the leading and trailing edges of the sheets are at small angle to the cutting blade so that the edges of the laminated sheets have an unattractive uneven appearance.
The prior art has utilized light sources and photocell sensors to vary the lateral and rotational position of an article severing means, like a punch, to properly align the edges of the punch and the article. U.S. Pat. No. 4,541,317 is an example of this prior art. However, the prior art photocell system for automatically positioning the cutting device relative to the straight edges of the article to be severed from the webs have left much to be desired from the standpoint of ease of operation and adjustment of these systems and the reliability and accuracy of the cutting operation.